Radio frequency (RF) communication systems that make use of frequency division multiplexing (FDM) are known. In such systems, commonly known as trunked communication systems, communication channels are assigned for use from time to time to subscribers as needed.
RF systems that make use of time division multiplexing (TDM) are also known. In these systems a communication frequency (or pair of frequencies) is divided by time into frames and slots, and subscribers are assigned a slot to support their communication needs.
Combined FDM/TDM systems are also known. In such systems, a subscriber will be assigned a particular time slot on a particular frequency (or pair of frequencies) to support its communication needs.
FDM/TDM systems offer a number of advantages versus FDM systems in regard to support for many desirable features. Additional information regarding these features and their implementation within an FDM/TDM system can be found in a commonly owned co-pending application U.S. Ser. No. 300,392 filed on even date herewith. Therefore, introduction of TDM into existing FDM systems is highly desirable.
It would be impractical, however, in many systems to immediately convert all current FDM-only users to TDM communications. A need exists for a communication system that will economically support communication needs of both FDM-only communication users and TDM communication users.